Abstracts Category : Other

Evaporation of Water in Hydrophobic Confinement

by Mohsen Ghasemi

Evaporation of water in hydrophobic confinement hasbeen a subject of numerous studies because of its key role infunctioning and self-assembly of many biologically relevantsystems, such as protein folding, formation of lipid bilayers,operation of ion channels, etc. Evaporation is an activated processand hence is a rare event in molecular time-scales. There is noconsensus on a continuum thermodynamic theory which capturesdifferent aspects of the process satisfactorily. We study thesimple case of evaporation of water confined between two rigidhydrophobic walls of tunable hydrophobicity, and adopt nucleationtheory as our continuum thermodynamic approximation. We proposeanalytical expressions for free energy barrier and size of thecritical vapor tube necessary for evaporation to occur. In thetheory, we incorporate the effect of line tension, that has beenneglected so far. To validate the expressions and explore role ofline tension, we obtain free energy barriers and critical radii toevaporation from molecular simulations, by employing IndirectUmbrella Sampling (INDUS) and committor probability analysismethods. By comparing the results from simulations and theory, wefind that the role of line tension is crucial in evaporation ofwater in hydrophobic confinement.Advisors/Committee Members: Sharma, Sumit (Advisor).